Merge pull request #69 from Roshyo/patch-1

Thank you @Roshyo !

Author: bartoszpietrzak1994

src/Ui/Action/DownloadInvoiceAction.php

@@ -52,7 +52,7 @@ public function __invoke(Request $request, string $id): Response
         ));
 
         $response->headers->add(['Content-Type' => 'application/pdf']);
-        $response->headers->add(['Content-Disposition' => $response->headers->makeDisposition('attachment', $filename)]);
+        $response->headers->add(['Content-Disposition' => $response->headers->makeDisposition('attachment', $filename . '.pdf')]);
 
         return $response;
     }